This invention relates to control and monitoring systems for dual-fuel engines.
Gaseous fuels such as various grades of natural gas and gaseous derivatives of various forms of hydrocarbons have been used in combination with liquid hydrocarbon fuels such as low-end hydrocarbons, commonly known as diesel or jet fuel, and high-end hydrocarbons, commonly known as gasoline, in compression-ignition engines particularly, and to some extent in electrical-ignition engines. Because of their gaseous state, the gaseous hydrocarbon fuels mix more thoroughly with air oxidizer and, therefore, combust more completely, faster and generally at higher temperatures than the liquid hydrocarbon fuels, even though their density of hydrocarbons is lower than for liquid hydrocarbon fuels. Additionally, the higher speed and completeness of combustion of the gaseous hydrocarbon fuels aids completeness and speed of combustion of the liquid hydrocarbon fuels. Results include (a) increased output power from relatively low-cost and globally more abundant gaseous hydrocarbon fuels, (b) increased power per consumption of the liquid hydrocarbon fuels, (c) lower exhaust pollution, and (d) conservation of less abundant liquid hydrocarbon fuels that generally cost more to produce.
Engine problems occur, however, in relation to control of dual-fuel systems. A major problem is the higher combustion heat related to the advantages of dual fuel. The control problems are preventable with sufficient monitoring and regulation of the particular engine functions, including ultimately terminating supply of the gaseous fuel without shutting off the engine in the event of higher combustion heat than supportable by a cooling system of the engine.
There are known means and methods for monitoring and controlling dual-fuel engines, but none with the effectiveness, reliability and low cost made possible by this invention.
Examples of different but related monitoring and control technologies for dual-fuel engines are described in the following patent documents. U.S. Pat. No. 5,890,459, issued to Hedrick, et al. on Apr. 6, 1999, described a dual-fuel engine having three separate injectors in diesel-engine cylinders for separately timed and controllably metered injection of diesel fuel and gaseous fuel. U.S. Pat. No. 5,370,097, issued to Davis on Dec. 6, 1994, described a dual-fuel control system and method having an actuation controller of gaseous and liquid fuel conveyed to an internal-combustion engine in response to a sensor of rotational speed and a sensor of exhaust temperature of the engine. U.S. Pat. No. 5,379,740, issued to Moore, et al. on Jan. 10, 1995, described a dual-fuel, pre-compression injection system and method for controlling flow of liquid and gaseous fuel through the same lines into an engine inlet manifold from separate tanks. U.S. Pat. No. 4,909,209, issued to Takahasi on Mar. 20, 1990, described injecting LP gas from an LP cylinder into a diesel-engine air inlet through an injector nozzle in response to minimum engine heat and rotational speed. U.S. Pat. No. 4,641,625, issued to Smith on Feb. 10, 1987, described a computerized control system for controlling injection rates of liquid and gaseous fuel to a dual-fuel engine. U.S. Pat. No. 4,619,240, issued to Bedford, et al. on Oct. 28, 1986, described control of dual-fuel injection rates by computerized control in response to pressure in a fuel line for primary fuel intermediate a fuel pump and an injector. U.S. Pat. No. 4,603,674, issued to Tanaka on Aug. 5, 1986, described control of rates of injection of gaseous and liquid fuels to a dual-fuel engine in computerized response to difference between actual engine speed and a predetermined rate of speed per rate of injection of a primary fuel. U.S. Pat. No. 4,597,364, issued to Young on Jul. 1, 1986, described timing injection of a gaseous fuel into cylinders that are next in line for combustion. U.S. Pat. No. 2,714,883, issued to Metzger on Aug. 9, 1955, described means for stopping a dual-fuel engine by shutting off all fuel in order to purge the engine as a result of failure of any one of a plurality of engine components or functions such as low oil pressure, excessive water-jacket temperature, excessive rotational speed and failure of air supply.